I have a '91 M5 and have been quite frustrated in trying to fix wiper blades. I wanted to maintain the orginal wiper blade(with the little spoiler) and replace just the rubber but those things are hard to put on and those little metal strips continually fall off. I think they were designed just to piss people off. As you try to slide them up, the rubber inevitably becomes misaligned with the metal strip.
KJK 91 M5